A boarding bridge is a passage which connects an airport terminal gate to an airplane in order for passengers to safely board the airplane. The boarding bridge has a two-tiered tunnel structure including an inner tunnel and an outer tunnel or a three-tiered tunnel structure in order to be safely connected to the airplane according to whether or not the airplane is moored and a location of the airplane.
In the boarding bridge, there is a difference in height between a floor surface of the inner tunnel and a floor surface of the outer tunnel. There may be a large step difference of about 25 cm between the inner tunnel and the outer tunnel. Accordingly, the inner tunnel and the outer tunnel are provided with an inclined foot plate at a location where the step difference is formed.
However, due to the large step difference between the inner tunnel and the outer tunnel, the foot plate has a high gradient, which gives passengers inconvenience in movement. Particularly, it is impossible for a passenger using a wheel chair to move by him/herself. As for ordinary people, they have the risk of falling down and thus suffering fractures due to a steep gradient.
Regarding a conventional apparatus for reducing a step difference formed between an inner tunnel and an outer tunnel, Japanese Patent No. 4700643 (entitled “Boarding bridge”) discloses a boarding bridge in which a step difference between an outer tunnel and an inner tunnel is eliminated by a variable-length passage which is wound or pulled out by rotating a sprocket along with a movement of the outer tunnel.
However, the conventional boarding bridge includes many components including a partition plate constituting the variable-length passage, a partition plate supporting part, a chain for moving the variable-length passage, and the sprocket, and has a complicated structure. Thus, it is difficult to install the conventional boarding bridge.
Since the conventional boarding bridge includes many components for operation, its failure rate is increased. When one of the components is broken, the whole structure needs to be disassembled. Therefore, it is not easy to maintain and repair the conventional boarding bridge.
Further, since the variable-length passage includes the partition plate, it is difficult to manufacture the variable-length passage to have a high stiffness. Thus, it is not suitable for many passengers to use at a time.